Improving Survival and Health of Lumpfish (cyclopterus Lumpus L.) by the Use of Feed Blocks and Operational Welfare Indicators (owis) in Commercial Atlantic Salmon Cages

To investigate possible differences survival and welfare of lumpfish fed either feed blocks or commercially available pelleted feed in commercial cages, eight 90 m polar circle cages containing approximately 50,000 Atlantic salmon with a mean weight of 2 kg were stocked with 3800 lumpfish with a mean weight of 52 g in each cage. Four of the cages were fed with a standard commercial pelleted feed and four with feed blocks. Growth was significantly lower for fish fed feed blocks although both feed types were offered at a daily feeding rate of 1.5% BW−1 based on biomass gain. There were differences in the number of mortalities recorded between the two treatments with fish fed with pelleted feed had higher mortality and was more sensitive towards mechanical treatment that occurred during the study period. Operational welfare indictors (OWI) were developed to assess health and condition for lumpfish. The OWIs showed a lower score in the feed block group indicating better health status in this group. Overall, the findings of the present study show that feed blocks can give more controlled growth, increased survival and better overall health status of lumpfish in sea pens with Atlantic salmon.